Rules
In top-flight competition, service is decided by a coin toss. At lower levels it is common for one player (or the umpire/scorer) to hide the ball in one or the other hand (usually hidden under the table), allowing the other player to guess which hand the ball is in. The correct or incorrect guess gives the "winner" the option to choose to serve, or to choose which side of the table to use. In recreational games, the players may have a rally for a minimum set number of hits, after which the rally is played out, with the winner either choosing to serve or choosing the table side. Others use the "P-I-N-G" method rallying back and forth spelling a letter of P-I-N-G after every hit. After P-I-N-G is spelled the person to win the rally also wins the serve. In game play, the player serving the ball commences a point. Standing behind the end of the table, with the ball in the palm of one hand - over the table's height - and the bat in the other, the server tosses the ball without spin, upward, at least sixteen centimeters (approximately 6 inches). He or she then must hit the ball such that it bounces once on his or her half of the table, and then bounces at least one time on the opponent's half. If the ball strikes the net but does not strike the opponent's half of the table, then a point is awarded to the opponent. However, if the ball hits the net, but nevertheless goes over and bounces on the other side, it is called a let. Play stops, and the ball must be served again with no penalty. A player may commit any number of lets without penalty. If the service is "good", then the opponent must then make a "good" return — by returning the ball before it bounces on his or her side of the table a second time. Returning the serve is one of the most difficult parts of the game, as the server's first move is often the least predictable. Points are awarded to the opponent for any of several errors in play: Allowing the ball to bounce on one's own side twice Not hitting the ball after it has bounced on one's own side Having the ball bounce on one's own side after hitting it Hitting the ball before it has bounced on one's own side of the table,(i.e. making a volley) except if it is clearly on the outside of the table when it is hit. Double hitting the ball. Note that the hand below the wrist is considered part of the bat and making a good return off one's hand or fingers is allowed, but hitting one's hand or fingers and subsequently hitting the racket is a double strike and an error. Allowing the ball to strike anything other than the racket (see above for definition of the racket) Causing the ball not to bounce on the opponent's half (i.e., not making a "good" return) Placing one's free hand on the playing surface or moving the playing surface Offering and failing to make a good serve (i.e., making a service toss and failing to strike the ball fairly into play) Making an illegal serve: one deemed outside the rules (e.g., one preceded by a player's hiding the ball or his failing to toss the ball at least 16 centimeters (six inches) in the air. Alternation of service Service alternates between opponents every two points (regardless of winner of the rally) until a player reaches 11 points with at least a two-point lead, or until both players have 10 points a piece. If both players reach 10 points, then service alternates after each point, until one player gains a two-point advantage. In doubles, service alternates every two points between sides, but also rotates between players on the same team. At the end of every two points, the receiving player becomes the server, and the partner of the serving player becomes the receiver. In the old 21-point game system, service would alternate every 5 points. If both players reached a score of 20, then service would alternate each point until one player gains a two-point advantage. After each game, players switch sides of the table and in the fifth or seventh, game "for the match", players switch sides when the first player scores 5 points, regardless of whose turn it is to serve. In competition play, matches are typically best of five or seven games. Some recreational players may choose to use a volleyball style system of scoring and play. Such variations include, but are not limited to, allowing the let serve, not requiring the server to hit the ball on his half of the table first (but still allowing it), allowing the volleying of returns, and relaxing other small rules in doubles to make the game easier to play. Common recreational scoring styles include best-of-three-game side out scoring to 15, 21, 25, or 30 points per game with a third game being played rally style to 15; best-of-five-game rally style play with each game, save the fifth (to 15), played to 30 points; and traditional tennis scoring. In addition to games between individual players, pairs may also play table tennis. In doubles, all the rules of single play apply except for the following. A line painted along the long axis of the table to create doubles courts bisects the table. This line's only purpose is to facilitate the doubles service rule, which is that service, must originate from the right hand "box" in such a way that the first bounce of the serve bounces once in said right hand box and then must bounce at least once in the opponent side's right hand box (far left box for server). Play then continues normally with the exception that players must alternate hitting the ball. For example, after a player serves the receiving player make his or her return, the server's partner returns the ball and then the service receiver's partner would play the ball. In wheelchair doubles table tennis, a player hits when the ball reaches their side. The point proceeds this way until one side fails to make a legal return and the point is then awarded to the other team. Also, when the game reaches the final set, the teams must switch side and the team that receives the service must switch receiver when one of the teams reach 5 points. Singles and doubles are both played in international competition, including the Olympic Games since 1988 and the Commonwealth Games since 2002. In 2005, the ITTF has announced that doubles table tennis will only be featured as a part of teams events in the 2008 Olympics.